The invention relates to a system for supporting a guidewire that is advanced towards a predetermined position in a vascular system of a human or an animal.
Percutaneous coronary intervention procedures are used to treat patients with diseased arteries of the heart such as stenosis caused by a build-up of fats, cholesterol and other substances from the blood (referred to as plaque) that severely restricts or (almost) blocks blood flow.
PCI may be performed by threading a catheter, along a path previously defined by bringing a guidewire to the position of the stenosis, from an artery in the groin to a position in an artery of the heart. This is known as percutaneous transluminal coronary angioplasty (PTCA), coronary artery balloon dilation or balloon angioplasty. The balloon is then inflated, compressing the plaque and dilating (widening) the narrowed coronary artery so that blood can flow more easily. To maintain the dilated section of the blood vessel open, an expandable metal stent may be expanded by the inflating balloon and left in place as the balloon is retracted after deflation.
In the event of a heart attack, it may be required that the blocked artery is opened quickly by inflating a small balloon and inserting a stent to restore blood flow to the heart muscle within 90 minutes of the patient's arrival at the hospital. PCI in such emergency circumstances is referred to as “primary” PCI. Other PCI procedures, such as those done to unblock an artery before a heart attack occurs, are referred to as “elective” PCI.
The number of complex stenotic lesions to be treated is growing. At present, about 25% of the PTCA treatments involves the treatment of such complex stenotic lesions. Complex lesions are for instance lesions with calcification, lesions that are far from the point of entry into the patient and diffuse lesions of which the boundaries are difficult to locate precisely.
Passing a guidewire through a complex stenotic lesion (also referred to as crossing of the lesion) is one of the larger challenges for interventionists. Crossing complex lesions involves two main problems: safety of the patient and costs of the treatment.
For crossing non-complex stenotic lesions, a guidewire having a soft and/or flexible tip is used. Because of the flexibility of the tip, the risk of causing complications, such as perforation of the wall of the vessel is small. However, crossing a complex stenotic lesion conventionally requires the use of a guidewire having a more rigid tip; the more complex the lesion, the more stiff and/or sharp the tip of the guidewire needs to be to successfully cross the lesion. A disadvantage of a guidewire having a stiff tip is that it is more difficult to navigate the guidewire through tortuous vascular sections.
Cardiologists use contrast liquid and X-ray imaging to obtain a fluoroscopic image of the structure of the coronaries of a patient. During the procedure contrast liquid needs to be injected at regular intervals to maintain good vision during the procedure, especially during complex procedures. However, it is in the interest of the patient's safety to keep dosages of contrast liquid and X-ray radiation low. Repeated exposure to stray levels of X-ray radiation also constitutes a hazard for medical personnel.
The safety of the patient is also related to the duration of the procedure. The longer the procedure, the higher the risk of complications, such as the formation of thrombosis on the devices inserted into the patient. Complex procedures generally take substantially more time than straightforward procedures and therefore inherently entail an increased risk of complications.
Treatment of a complex stenotic lesion requires a cautious approach involving the introduction of several guidewires before a lesion can be crossed. On average, the time required for crossing a complex stenotic lesion constitutes more than 80% of the overall duration of the procedure while the available amounts of time of catheterization facilities and cardiologists is typically limited. Thus, longer procedure times directly affect costs and the duration of waiting periods for patients to be treated.
For instance, although chronic total occlusions (CTOs) are frequently found in patients who undergo coronary arteriography for known or suspected coronary artery disease, only a few of these lesions (5.7-9.4%) are treated by PCI. The reason for this low number may be due to the low success rate of PCI, as well as the high procedural cost and high radiation exposure for both patients and operators (J. D. Abbott et al.; Recent trends in the percutaneous treatment of chronic total coronary occlusions; Am J. Cardiol. 2006; 97:1691-6). The most common reason that PCI fails in patients with CTO is the inability to pass a guidewire across the occlusion into the distal vessel (M. Ochiai; Retrograde approach for chronic total occlusions: present status and prospects; EuroInterv. 2007:3:169-173). An increased success rate in the treatment of CTOs would result in applicability of PCI to a larger number of cases.
In view of the increasing numbers of treatments of complex stenotic lesions and the problems regarding patient safety, costs and, in some countries, waiting time, there is an important need for solution which allows to cross complex lesions more safely and more quickly. Current specialized methods for the treatment of complex stenotic lesions have seen limited success and are not suitable for the average cardiologist.
Similar problems arise in the crossing of constrictions or occlusions in the course of percutaneous treatment of other endovascular diseases and neurovascular disease treatment.